This invention is in the field of surgical devices that will be implanted into human or animal bodies, for uses such as repairing or replacing cartilage in joints such as knees or hips, or for repairing injuries to tendons, ligaments, or other connective tissues.
Efforts have been made to design and create various types of surgical devices called “knotless suture anchors”. A subgroup of such devices which are of interest herein are designed to attach soft tissues (such as ligaments or tendons) to hard bones. These are used mainly by orthopedic surgeons, and by other physicians who specialize in “sports medicine”. These practitioners make every effort to minimize any cutting of (and any damage to) the tendons, ligaments, muscles, blood vessels, and other soft tissues that surround injured, diseased, or otherwise damaged or defective tissue, especially in and around articulating joints. Therefore, any steps that can be taken to minimize the number and the lengths (or sizes) of any incisions and cuts that must be made, during arthroscopic or other surgical repair of joints and other structures, are regarded as useful and helpful.
In addition, orthopedic surgeons are under pressure to work as quickly and efficiently as possible, starting when a patient's skin has been cut or punctured by the first instrument, and lasting until the patient's joint, limb, or body has been closed up and covered with bandages. As a general principle, the longer a patient's body or limb stays open, the greater will be the risk, threat, and likelihood of infection.
Accordingly, the requirement of having to tie knots in suture strands, when the only instruments that can be used are long arthroscopic instruments that are narrow enough to pass through a small arthroscopic incision, can pose difficult challenges. These challenges become especially complex, when one realizes that typical arthroscopic surgery requires, in addition to the actual surgical instruments, a number of supporting devices, which in most cases will include: (i) a light source; (ii) a camera with a live video feed, which normally will use fiber-optic cables; (iii) a tube which will continuously pump clear saline liquid into the joint or other operating area, to carry blood and debris out of area so that the surgeon can see the structures and tissues that are being manipulated; and, (iv) a drainage catheter or cannula, to suction the saline liquid and its contents out of the joint or body cavity.
Under those conditions, the challenge of tying a knot in a suture strand, especially in a location that may be on the far (distal) side of a bone or other anatomic structure, using only a single elongated instrument tip, can become be extremely difficult, and can be compared to trying to tie a set of shoelaces into a tight and secure knot, using a set of needle-nosed pliers that can be touched by only one hand.
Surgical staples can be well-suited for securing soft tissues to other soft tissues, but they are not suited for securing soft tissues (or suture strands which have been attached to soft tissues) to hard bone surfaces. When attachments to hard bone are required, more secure devices, usually called anchors, are used instead of staples. Some are designed to be screwed or tapped into a “pilot hole” that has been drilled into a bone; others are driven directly into a bone surface, in a manner comparable to driving a nail into a board with no pilot hole.
Accordingly, surgeons and orthopedic supply companies have developed various types of “knotless suture anchors”, which enable surgeons to attach suture strands (which, in most cases, will be attached to soft tissues, and which can thereby provide convenient “handles” that can be used to pull, stretch, pin down, or otherwise manipulate the soft tissues) to hard bone surfaces. These types of knotless suture anchors are described and illustrated in a number of issued patents and published patent applications, which can be divided into several categories, for purposes of analyzing and understanding them.
A first category involves anchors that will undergo some type of shape alteration, after they have been inserted into a drilled hole, in a manner which will cause a set of projections to extend outwardly from the main body of the anchor. The projections will press against or dig into the walls of the pilot hole in the bone, thereby firmly securing the anchor to the bone and preventing it from being pulled out by any tensile forces which are likely to be imposed on the suture strand. On some of these types of anchors, the projections have spring-type or angled structures that are similar to the “barbs” on a harpoon or fishing hook; on other anchors in this category, the projections are more closely comparable to the types of “expander bolts” that are used to mount large paintings and other heavy wall-hangings to drywall in homes and other buildings. Issued patents which describe these types of suture anchors include, for example, U.S. Pat. No. 6,328,758 (Tornier et al 2001), U.S. Pat. No. 7,144,415 (Del Rio et al 2006), and U.S. Pat. Nos. 7,556,640 and 7,695,494 (both by Foerster et al, 2009 and 2010).
A second category of knotless suture anchors include two components which are separate from each other before installation. Because of how they interact and function, the two components can be regarded as a receptacle, and an insert. In this type of design, the receptacle component is implanted into a bone, normally into a pilot hole. After the receptacle component has been fully inserted into the bone, the insert component is inserted into the receptacle, typically using tapping, screwing, or similar efforts to drive the insert far enough into the receptacle to lock them together. In some of these anchors, the receptacle component will be fully anchored to the bone, before the insert component is emplaced in the receptacle; in other designs, the act of forcing the insert into the receptacle will cause a shape change which completes the anchoring of the receptacle to the bone.
In these types of knotless suture anchors, a suture strand typically is looped around, passed through, or otherwise coupled or affixed to the insert component, before the insert component is inserted into the receptacle. In some designs, the act of driving the insert into the receptacle will squeeze, crimp, or otherwise secure the suture strand to the anchor, in a manner which cannot be altered later without difficulty; an example of this type of design is provided by U.S. Pat. No. 7,572,283 (Meridew 2009). In other designs, a yielding elastomeric fit between the insert and the receptacle will allow subsequent adjustments to the suture strand, if a tensile force is exerted on the strand which exceeds some type of “threshold” force level; this design is illustrated in several published applications by McDevitt et al, such as US 2003/0130695. Still other designs enable the insert component to be manipulated in a way that will allow the receptacle component to be removed from the bone, if needed, in case the tension on the suture strand which is held by that anchor needs to be adjusted after an initial fixation; this type of design is illustrated by U.S. Pat. No. 6,540,770 (Tornier et al 2003).
Other designs for knotless suture anchors with various other traits are provided by a number of other issued patents and published applications, which include, for example, U.S. Pat. Nos. 6,520,980; 6,585,730; 7,682,374; and 7,637,926, all issued to Foerster et al and assigned to either Opus Medical Inc. or ArthroCare Corporation.
A different type of design, which involves a ratcheting suture anchor, is described and illustrated in two published patent applications, US 2010/0063542 and 2010/0121348, both by Van Der Burg et al. In this design, a suture strand is wrapped around an internal component which can rotate, in a ratcheting manner, within an outer sleeve component. The ratcheting mechanism is provided by a pin, affixed to the top of the rotating internal component, which travels along a sawtooth surface provided by the outer sleeve. The pin can “ride up” each sloped incline on the sawtooth surface. Each time it reaches the top of an incline, it will drop down a steep edge, into a settling location. This effectively prevents the ratchet mechanism from traveling in the non-allowed direction, unless the surgeon takes special steps to disengage the pin from the sawtooth surface so that the tension on the suture strand can be adjusted.
Since this current invention involves different designs for ratcheting suture anchors, the two published Van der Burg applications establish the closest and most directly relevant prior art which is known to the applicant herein.
The types of ratcheting suture anchors disclosed herein were initially conceived and developed, as part of an effort to develop a complete system for a very different type of surgical operation, which involves replacing cartilage segments in joints such as knees, rather than reattaching tendons to bones for purposes such as rotator cuff repair. Because of certain operating requirements and constraints that arise in the types of cartilage repair operations being developed by the Applicant herein, he began with a completely different design, compared to the approach disclosed by Van der Burg et al. Subsequently, after locating and reviewing the Van der Burg applications, the Applicant herein realized that there are major differences in the two approaches to creating ratcheting suture anchors, and that the designs disclosed herein can offer a number of advantages, compared to Van der Burg's approach.
To adequately explain how and why the Applicant's designs took a different approach and arrived at a different set of solutions to a set of challenges and obstacles, some additional background information is required, on how injured or diseased cartilage segments are repaired, in load-bearing joints such as knees and hips.
Hyaline, Meniscal, and Labral Cartilage Segments in Joints
Two different classes of cartilage are essential for the proper functioning of articulating joints. The type of cartilage known as hyaline cartilage forms a relatively thin coating layer of soft and lubricated tissue that covers a “condylar” surface of a bone, in a joint. Two or more segments of hyaline cartilage, on the surfaces of different bones in a joint, will press, rub, and slide against each other, during motion of the joint. Any segment of hyaline cartilage will necessarily have: (i) an “articulating” surface, which is smooth and slippery, and which is kept wet and lubricated by synovial fluid; and, (ii) at least one “anchoring” surface, which create a strong and stabilized interface (reinforced by numerous fibrous proteins and similar components) between the supporting hard bone structure, and the softer layer of cartilage.
Meniscal cartilage is more complicated. Each knee joint contains two meniscal segments, which are generally wedge-shaped arcs that are positioned on the inner (medial) and outer (lateral) sides of the uppermost “plateau” of a tibial bone (i.e., the shinbone). These two wedge-shaped arcs help constrain the femoral bone (i.e., the thighbone), and they help prevent unwanted lateral movement of the femur, across the tibial plateau. Accordingly, the two meniscal segments are not thin layers of cartilage which coat a bone surface; instead, they are fibro-cartilage segments with substantial thickness, and they are kept in position in a “floating but tied down” manner which presses against and stabilizes the medial and lateral sides of the femoral bone. This anchoring attachment is created by a combination of: (i) tendon-like fibrous strands which emerge from both tips of each meniscal arc, and which are attached to bony protrusions located in the middle of the tibial plateau; and, (ii) additional fibers which attach the rounded outer surfaces of the meniscal segments to the soft membranous tissue which forms a watertight capsule that encloses the knee joint. In addition, the geometric structures of the bones also help stabilize the knee joint. Those bone structures include: (i) a “double-roller with center groove” shape, at the bottom condylar end of a femur bone; (ii) an elevated “spine” component in the center of the tibial plateau, which interacts with the center groove on the femoral condyle; and, (iii) a “scalloped” shape on the posterior side of the kneecap (patella), which presses and slides against the double-roller surface on the femur bone.
In addition to meniscal cartilage in knee joints, hip and shoulder joints contains similar relatively thick fibrocartilage segments which are anchored to bones, mainly by indirect means involving tendon-like fibrous supports. Those types of cartilage segments in hip and shoulder joints are called labrum segments, or labral cartilage. For various reasons, they do not require repair or replacement as often as meniscal cartilage segments in knee joints; nevertheless, they do sometimes become injured or degraded, usually in connection with other problems that arise in hip or shoulder joints, and they sometimes need to be surgically repaired or replaced. Because of the structural similarities between meniscal cartilage segments and labral cartilage segments, labral cartilage is regarded and referred to herein as a subtype or subclass of meniscal cartilage, and any references herein to methods or devices for repairing or replacing meniscal cartilage are intended to also cover and include methods and devices for repairing or replacing labral cartilage segments, in hips or shoulders.
It also should be understood that “articulating” joints require two or more bone surfaces to be able to press, move, and slide relative to each other, in a lubricated and frictionless manner. By contrast, certain other types of cartilage, which are present in non-articulating structures such as spinal discs, ears, noses, and windpipes, do not have articulating surfaces. Those types of cartilage are very different (both structurally and functionally) from hyaline and meniscal cartilage, and the design and implantation requirements that arise, when non-articulating cartilage segments are being repaired or replaced, are very different from the requirements that apply to implants that will be used to repair or replace hyaline or meniscal cartilage.
Accordingly, any references herein to “cartilage” are limited to articulating cartilage (i.e., to hyaline, meniscal, or labral cartilage), and any prior art devices which have been developed for repairing or replacing non-articulating cartilage (such as in windpipes, ears, or spinal discs) are regarded as not relevant to this invention, since the structural and functional requirements and constraints that arise in the repair of non-articulating cartilage are so different from articulating cartilage.
Because hyaline and meniscal cartilage segments do not have a normal blood supply, and because they are subjected to compressive and shearing forces and stresses whenever a joint is moved, it is very difficult and in most cases impossible for cartilage to heal and recover, if it becomes abraded, injured, diseased, or otherwise damaged. Therefore, a huge amount of effort has been devoted to developing implant devices that can be used to permanently replace segments of cartilage that have been damaged.
One set of efforts which require attention herein has been carried out by the Applicant herein, Kevin Mansmann, an orthopedic surgeon who works in Pennsylvania. As described and illustrated in a number of issued patents and published applications, Dr. Mansmann has been focusing on designing, developing, and testing cartilage-replacing implant devices that contain synthetic “hydrogel” polymers.
As suggested by the name, “hydrogel” polymers hold and contain water. In the types of polymers that are of interest herein, chemical reactions are used to convert “monomer” reagents into polymerized molecules which have long “backbone” chains, with specialized side groups that are bonded to the long backbone chains. The relatively short “side groups” can also be called pendant groups, short chains, or similar terms, and in some cases they form covalent “bridges” which will connect different backbone chains to each other. A wide variety and assortment of side groups can be incorporated into polymers, by proper selection and control of the monomer reagents that will be used to make a polymer, and the lengths, densities, and other features of the side groups will determine the physical and performance traits of any particular polymer formulation (such as, for example, whether a polymer is hydrophobic or hydrophilic; whether it is hard and rigid, or soft and pliable; and, whether it is dense and compacted, or porous and able to absorb and hold water).
Accordingly, the ability to select from a wide range of candidate monomer compounds, which can incorporate various types of “side” chains or groups into a final polymerized compound, enables technicians to create synthetic polymer compounds which can function as hydrogels that can contain nearly any level of water content that is of interest. The water content of a hydrogel polymer can be expressed as a percentage (based on either weight, or volume) which is occupied by water rather than polymer molecules. Since percentages measured by weight are easier to determine (i.e., by simply comparing the weights of water-saturated polymer segments, versus dehydrated polymer segments), weight percentages are used more commonly, to compare and define different versions and formulations of the types of polymers of interest herein.
Essentially all of the cartilage-replacing surgical implant devices that are being manufactured and sold today with polymeric components use relatively hard and dense plastics which do not contain water, and which are not “hydrogel” polymers. Most such implants use a polymer called “ultra-high-molecular-weight polyethylene” (abbreviated as UHMWPE), especially in any “load-bearing” joints that need repair, such as knees and hips. Since the presence of any internal water, in any polymer, will necessarily and unavoidably lead to reduced strength and durability of that polymer (compared to water-impermeable hard plastics), the desire of orthopedic implant companies to provide the strongest and most durable implant devices that can be designed and manufactured, using modern technology, has generally led those companies to select and use water-impermeable polymers, for implant devices designed for load-bearing joints such as knees and hips.
However, hydrogel polymers (i.e., polymers which will absorb and hold a significant quantity of water, within the molecular framework or lattice which forms a polymeric material) are becoming of substantial interest for implant devices designed to replace cartilage, because of two important reasons.
First, synthetic hydrogels have the potential to emulate natural cartilage, much more closely than the types of hard and dense polymers that are used for conventional knee or hip replacements. Natural cartilage is a hydrogel material; it contains a relatively high water content, and the ability of the water molecules to move, travel, and dynamically redistribute themselves, in response to changes in localized pressures or stresses within a lattice or matrix of collagen fibers that form cartilage, plays an important role in the ability of cartilage to perform in its normal and desirable manner, whenever a joint is being moved and used.
A second major potential advantage of hydrogel polymers, compared to hard plastics, is that hydrogels can be much more flexible than hard plastics. As a result, hydrogel components offer the potential for creating relatively large implant devices that can be rolled into a cylindrical shape, inserted into a joint via an arthroscopic insertion tube (which can have roughly the diameter of a finger or thumb), and then unrolled or otherwise expanded into a final desired shape, after the implant has reached the interior of the joint that is being repaired. That type of arthroscopic repair inflicts much less damage and disruption on the muscles, tendons, blood vessels, and other soft tissues that surround a joint, compared to the types of surgery used to insert implants with hard plastic and metal components, in conventional knee or hip replacements.
As a result, orthopedic implant companies continue to monitor any advances that are being made in the development of stronger and more durable hydrogel polymer materials. Those companies are fully aware that if hydrogel polymers can be made with sufficient levels of toughness and durability to last for decades, even in load-bearing joints such as knees or hips, implants containing those types of polymers could provide not just one but two major advantages: (1) the flexible implants that hydrogels can help create would enable various types of arthroscopic repair of damaged joints, which cannot be accomplished when non-flexible hard plastic components are used; and, (2) hydrogel-containing synthetic polymers can emulate natural collagen, more closely than can be accomplished by the hard and rigid plastics that are being used in cartilage-replacing implants today. Accordingly, the work being done by Mansmann, using certain types of flexible synthetic hydrogels that have unusually high levels of strength and durability, offers the potential to enable a complete hip or knee replacement, using entirely arthroscopic methods and devices.
Certain other not-yet-published patent applications filed by the same inventor herein disclose a design approach for flexible cartilage-replacing implants that contain hydrogel polymers, and which use flexible cables to enable improved anchoring of the implant devices. These types of flexible cables will be embedded within a molded flexible hydrogel polymer component, in a peripheral location which presumably (but not necessarily) creates a continuous loop that surrounds and encompasses the entire periphery of the implant device. One example of such an implant can be provided by an oval-shaped or otherwise elongated implant device that is designed to resurface (and to completely replace the native cartilage on) a femoral runner, on either the medial or lateral side (or compartment) of a femoral condyle, in a knee joint. This type of implant device can be molded in a manner which generates an enlarged peripheral component, referred to herein as an enlarged rim component. That enlarged rim component will be designed to fit, in an accommodating manner, into a groove which will be machined (with the aid of templates and/or a computer-controlled cutting or grinding tool) into a hard bone surface that is being prepared to receive and support the implant device.
After the native cartilage has been removed (by cutting, grinding, and suctioning) from a bone surface that is being surgically repaired, a groove having a controlled size and shape will be machined into the bone surface, in a location that generally surrounds and encompasses the area where the implant will be positioned. After that preparative work has been completed, the flexible implant device (which has been temporarily rolled into a cylindrical shape) will be inserted into the joint, via an arthroscopic insertion tube. Once inside the joint, the flexible implant will be unrolled to return it to its manufactured shape, and it will be secured to the bone. When the enlarged rim component of the implant settles into the peripheral groove that was machined into the bone surface, that engagement of two accommodating shaped surfaces will help secure and anchor the implant to the bone in a strong, stable, and secure manner that will be better able to resist compressive, lateral, and other types of forces and stresses that will be imposed on the implant when the knee, hip, or other joint is being used and moved by the person or animal.
Accordingly, a flexible anchoring cable, made of multiple strands of a high-strength polymer and/or a non-corroding biocompatible alloy, can be embedded within an enlarged peripheral rim structure, which will surround a flexible implant of the type described above. If that type of peripheral anchoring cable is embedded within the molded polymeric component of a flexible implant, then a set of suture strands, flexible wires, or similar components can be wrapped around the anchoring cable at a plurality of locations, and the suture strands or wires (which can have any desired length) will emerge from the molded polymeric device, at locations that are suitably spaced and positioned around the periphery of the implant device.
For purposes of discussion herein, it is assumed that the strands or wires that emerge from the molded polymeric component of the anchoring device will be in the form of a segment of braided cable, made of at least three and up to about ten relatively thin strands of material. Those strands presumably will be made of a high-strength biocompatible polymer, such as ultra-high-molecular weight polyethylene (UHMWPE), which is well known and widely used in connection with various types of surgical implants. For convenience, and to clearly distinguish these segments of braided cables from the main anchoring cable which is embedded within the implant device, these suture cable segments which emerge from the polymeric component of an implant device are referred to herein as braided suture segments (or strands), or simply as suture segments (or strands), for convenience.
Typically, both of the two ends of a braided suture segment will be “free” (typically with a length of several inches for each free segment), thereby making both ends readily accessible to a surgeon. The center portion of a suture segment will be wrapped around the anchoring cable segment that is embedded within the implant. That wrapping-type attachment preferably should use a plurality of “turns” of the suture strand, around the embedded cable, to reduce any risk of slippage or other relative motion of the suture strand inside the molded polymeric component.
This current patent application focuses primarily on the types of devices that can be used to secure, and adjust, the “free ends” of the suture strands that emerge from a polymeric component of a flexible cartilage-replacing implant. Those free ends will be attached, by the surgeon, to either hard bone or soft tissue in the vicinity of the implant, in a manner which will help stabilize and reinforce the implant.
When the Applicant herein began to consider and focus on the details of how a set of suture strands could be affixed to bone surfaces, to help anchor an implant device that would replace damaged cartilage in a joint such as a knee, his attention turned to knotless suture anchors. When he realized that none of the knotless anchor designs that are currently available would be optimal for the particular type of use he intended, he began to focus on how new and different types of knotless suture anchors could be designed, which would be optimized for that particular type of intended use.
Those analyses led him to conclude that a new design for “ratcheting” suture anchors can provide substantial improvements over all other currently known types of “ratcheting” or other suture anchors.
A full understanding of the preceding sentence will require some background information on ratchet mechanisms.
Rachet Mechanisms
Some sources assert that “ratchet” is the proper spelling for the mechanical components and systems discussed herein; however, other sources assert that “ratchet” is the proper spelling. Accordingly, both spellings should be regarded and accepted as alternate correct spellings.
In addition to having two different spellings, the term “ratchet” has acquired two different meanings Those different meanings can lead to confusion and conflict, if not fully understood.
A “classic” and relatively narrow definition of “ratchet”, which normally would be used by specialists such as mechanical engineers, requires the presence of both a gear and a “pawl”. This type of ratchet mechanism 20, which has been known for centuries in the prior art, is illustrated in a simplified form in FIG. 1, which is prior art, and which shows a rotating gear 22 having surface protrusions 24 (often called teeth, cogs, or similar terms). Under the classic and narrow definition, a ratcheting mechanism must also contain a “pawl” 26, which refers to any type of mechanism that will engage the teeth of the rotating gear in a manner that allows rotation in one direction, but not the other direction.
The designs of various types of interactive gears and pawls can become complex and sophisticated, and FIG. 1 is a simplified depiction of a basic mechanism. The pawl 26 is mounted on its own axle 27, and the operating end of pawl 26 is pressed against the teeth of gear 22 by the action of spring 28, which is mounted against a relatively stationary surface 29. The external spring is shown, solely for purposes of illustrating the basic arrangement; in nearly all types of pawl systems in use today, an internal (and therefore protected and unintrusive) coil spring is coupled to the axle of the pawl, to provide the same effect.
In a “classic” ratchet mechanism, the positioning and movement of the pawl constrains the travel of the gear, in a manner which allows the gear to rotate in only one direction. If a rotational force drives the gear to rotate in the direction shown by the block arrow in FIG. 1, the surface of gear tooth 24a will press against the side of pawl 26, in a way which will deflect pawl 26, causing it to rotate slightly about its axle 27 while spring 28 is compressed slightly. This allows gear tooth 24a to move “forward” and occupy the position currently occupied by tooth 24b in FIG. 1, which presses directly against the end of pawl 26.
A properly-designed pawl will not deflect and temporarily move out of the way, if the lower surface of gear tooth 24b presses against the end surface of pawl 26. In the depiction in FIG. 1, the axle-mounted placement of the pawl will allow the pawl to be deflected in a “sideways” (i.e., left-and-right) manner, but it will not allow the upper end of pawl to move in a “downward” direction. This is comparable to saying that if a conventional wagon is sitting on a sidewalk, it can be pulled horizontally, with relatively little effort, and it will simply roll, because of how its wheels and axles function. However, that same wagon cannot be pressed downward, into the sidewalk, without damaging and effectively breaking the wagon.
Ratchet mechanisms of this type are common and well-known. If desired, they can be modified in various ways, to adapt them for additional purposes. For example, in a so-called “ratchet wrench” (or ratcheting screwdriver), a V-shaped pawl with two arms can be mounted next to a gear, using an axle component that will allow either one arm of the pawl, or the other arm of the pawl, to engage the toothed gear at any particular time. In this way, operation of an external lever or other control device will allow the user of a ratchet wrench (or screwdriver) to set the tool in a first configuration that will tighten a bolt, nut, or screw when desired, and to subsequently change the setting of the wrench or screwdriver, so that it can loosen a bolt, nut, or screw.
Alternately, a ratchet wrench or screwdriver can have two separate and independent pawl components, and an external control lever will rotate an internal component which can push either pawl out of engagement with the gear, while allowing the other pawl to move into contact with the gear and engage it.
Accordingly, in the relatively narrow “classic” definition, a true “ratchet” system requires a gear, and at least one pawl component which can engage and constrain the gear in a manner that allows the gear to rotate in only one direction for as long as the pawl engages the gear.
However, a broader definition has emerged, which is widely and commonly used, and which is preferred and used herein. Since most users do not know or care what type of mechanism is being used to create a ratcheting effect, the term “ratchet” has come to include any mechanical linkage which allows motion in one direction (which can be linear, rotational, or any combination), while preventing motion in the “other” direction (which can also be called the opposite, prohibited, blocked, or non-allowed direction, or similar terms).
Yet another uncertainty can arise, in determining whether the term “ratchet” should:
(1) be strictly and narrowly limited, so that it applies only to devices and systems having mechanisms which completely block and prohibit motion in a “non-allowed” direction; or,
(2) be used in a more expansive and tolerant manner, to also include devices which can impede (or “strongly impede”) motion in a non-allowed direction, at a level which is sufficient to generally prevent such motion.
The types and classes of mechanisms which dwell in that zone of uncertainty, where it is not clear whether they do or do not properly and accurately qualify as “ratchet” devices or system, is illustrated and exemplified by the type of belt buckle that is often called a “cinch buckle”. This type of buckle, which is often found on woven or braided belts that are used to hold up trousers (cinch buckles normally are not used with leather belts or straps, since they would damage the leather), involves two metallic rings which are adjacent or close to each other, where they effectively become “parallel” circles or arcs. Each metal ring will have a portion (which can be a straight segment, within an otherwise circular ring) that is constrained within the webbing or fabric of the belt. When the free end of a belt is looped through a “cinch buckle”, the act of looping the belt over and around the “top” ring, before lacing it back through the lower ring and then pulling it tight (so that the rough or textured surface of a woven or braided belt will be pressed against itself) creates a squeezing and crimping force which pulls and presses the upper ring (and its loop of belt material) downward against the lower ring. In this manner, the two adjacent metal rings can squeeze and effectively grab a woven or braided belt, with sufficient strength to allow the belt to function adequately, in holding up trousers.
Accordingly, a cinch buckle can qualify as a ratcheting device, under a broad definition of “ratchet”, since it allows one end of a belt or strap to be pulled in one direction (i.e., in a tightening direction), and it then generally prevents that end of the belt or strap from traveling in the opposite direction (which would quickly loosen the belt or strap).
However, the fact that a cinch buckle can only generally prevent travel of a belt or strap in a non-allowed direction requires attention, because a cinch buckle does not have any mechanism which truly prevents and prohibits such travel (which is often referred to by terms such as slippage, creep, etc.). In general, a belt with a cinch buckle is adequate for holding up trousers, only if the person wearing the belt is able to conveniently and discretely reach down and tighten the belt when necessary to do so, during the course of a day or evening, each time the belt becomes too loose to function effectively. If desired, the surfaces of the rings can be have knurled or other rough or textured surfaces, which can help reduce slippage, but those types of steps do not change the nature of a cinch buckle.
To a large extent, the proper use of terms such as “ratchet” will depend on the setting, functional requirements, and context of the usage. For example, a cinch buckle might properly and reasonably be referred to as a ratchet mechanism, if used to secure a belt around a duffel bag or comparable item that is being used to store or transport clothes or other lightweight items.
However, a cinch buckle cannot be used to safely secure heavy cargo to a flatbed trailer, in the types of 18-wheeler trucks that haul cargo across highways. Since the risk of a cinch buckle gradually losing its “grip” on a strap or belt is so high, in an environment where vibration, jostling, or other repetitive motion occurs (and where unintended release of the cargo, from a truck driving at high speed down a highway) might kill or maim innocent people, it would constitute reckless disregard and even criminal neglect if a trucking company used “cinch buckles” on nylon straps to secure heavy cargo to truck trailers. Accordingly, in that type of setting, a cinch buckle should not be referred to as a ratchet mechanism.
Before moving on to a class of ratchet devices called “cam cleats”, it also should be noted that various types of ratcheting systems, devices, and designs are known, where it is not clear whether some particular mechanism does, or does not, comprise a gear-and-pawl system. As one example, in various types of devices (such as child-proof caps on pill bottles, in the lids of plastic pails that hold chemicals for swimming pools, etc.), a cylinder, disc, cap, or other rotatable component can be provided with a protruding “flap” or ramp-like structure on its periphery. When provided on the cap or lid of a container, that ramp-like structure usually is designed to rub against (and move across) a series of accommodating slots or ridges, which have been molded into the neck of the bottle, jar, pail, or other portion of the container, when the cap or lid is being tightened. Subsequently, if someone tries to remove the cap or lid, by rotating it in the opposite direction, the ramped structure on the cap or lid will “catch” on the slots or ridges of the bottle or pail, in a manner which will prevent rotation, unless certain additional steps are taken. Accordingly, this type of “safety” cap or lid can prevent a toddler from opening a bottle of pills, and it can prevent a pail of chemicals from coming open accidentally.
The point that should be recognized, in analyzing what might or might not qualify as a “true” or “classic” ratchet, is that some mechanical engineers would label the protruding component on such a cap or lid as a “pawl”, and would label the ridged or slotted components on the container as a “gear” (or gears), but other mechanical engineers likely would not agree that those “classic” terms should be stretched far enough to cover those types of devices.
Similarly, in the system illustrated in US application 2010/0063542 (Van Der Burg et al), a pin, which projects outwardly from a rotating internal component, interacts with a sawtooth surface on top of a cylindrical sleeve which surrounds the internal member (similar systems are widely used in retractable ballpoint pens, to allow an endless number of extensions and retractions of the ink point, by repeatedly pressing a button-type device mounted on top of the barrel of the pen). Some mechanical engineers might regard Van Der Burg's pin mechanism as a “classic” gear-and-pawl system, while others probably would not.
As shown by the various examples above, the narrow definition of “ratchet” systems (i.e., as being limited to “gear and pawl” systems) is not merely limiting, it is uncertain, potentially confusing, and difficult to apply and use consistently, when one realizes how many borderline cases might or might not be covered by the narrowly-defined “classic” definition. Therefore, the broader definition (i.e., to include any mechanical mechanism that is designed to allow travel of some component in one direction, while generally prohibiting and preventing travel of that component in the opposite direction) is clearer, and makes better logical and practical sense, and is preferred and used herein.
One example of ratchet linkages other than the classic “gear and pawl” linkage is provided by devices called “cam cleats”, which are commonly used on sailboats to temporarily secure ropes in certain positions. A cam cleat is generally depicted in FIG. 2, and better illustrations (including photographs of actual devices) are readily available in the online catalogs of companies that sell sailboat equipment.
The term “cleat” has been used for centuries, to refer to certain types of devices which are mounted on sailboat rails, and on docks, piers, and similar locations. Cleats are designed to enable ropes to be secured to them, without requiring a rope to be tied into a knot; alternately, if a knot is used to create a loop at the end of a rope, then that loop will effectively become a permanent part of that rope, and the knot will not need to be tied, and then untied, for each “cycle” of use.
There are powerful reasons, in sailing, for not wanting to have to repeatedly tie and untie knots in ropes. When large pulling forces are exerted on any knot (as often occurs whenever boats are involved, due to waves, tides, wakes from other boats, etc.), a knot that has been subjected to even a single moment of a large tensile force can be compacted into a very tight and hard configuration. It can be very difficult (or effectively impossible) to untie a knot which has been tightened to an extreme level of tightness and hardness, without tedious and extensive effort. Therefore, “cleats” were developed and designed as mechanisms that allow ropes to be secured to them, without requiring those ropes to be tied into knots.
In mechanical terms, “cam” refers to devices which generate some type of linear motion or travel when they rotate. This is usually accomplished by either of two types of designs. In one design, a gear or similar rotatable component (which might have either a smooth surface, or a toothed, textured, or other non-smooth surface), which has a genuinely circular shape, is affixed to a rotating axle, in some location other than the center of the gear. This creates an “eccentric” mounting of the gear, on the axle. As a result, each time the gear rotates through a complete revolution, while the axle is held in a constrained position, the “apparent” surface (or thickness) of the gear, when viewed from some particular angle, will generate a reciprocating (i.e., back-and-forth) linear motion, which can be imparted to a device such as a spring-mounted linear component.
The other main type of design for cam devices uses a rotating shape which is not truly circular. An example is provided by the “camshaft” devices used by automobile engines. A typical “cam gear” of this type has roughly the same elongated shape of a chicken egg, so that each time the camshaft rotates through a cycle, the “point” of each cam gear mounted on the camshaft will cause an engine valve to be displaced slightly, in a manner that will briefly open that particular engine valve. The inlet valves allow fuel or oxygen to enter a cylinder, in a manner that is precisely timed and controlled by rotation of the numerous non-circular gears on the camshaft, while the outlet valves allow the hot exhaust gases to exit the cylinders, at carefully synchronized moments in time.
Regardless of which type of design is used, cam devices are designed to cause “translational” (linear) motion of a surface which can rotate about an axle. Some cam devices make complete and multiple rotations (such as automobile camshafts), while other types of cam devices never complete a full rotational cycle.
A typical cam cleat, on a sailboat, has two gears, and neither gear is able to rotate through an entire circle. As indicated by the cam cleat mechanism 40, as shown in FIG. 2 (which is prior art), the two gears 42 and 44 are mounted on axle components 42a and 44a. Each axle incorporates a spring-loaded mechanism, to constantly exert a low-level force on each of the gears 42 and 44, which will constantly try to close the two gears together. The spring-generated force which attempts to close the two gears against each other will ensure that the ridges or “teeth” 42b and 44b of the two gears 42 and 44 will continually be pressed against the surface of rope 49, which passes between the two gears.
For simplicity of illustration, the surfaces of rope 49 are shown as being smooth. In practice, any such rope (usually braided from multiple strands of nylon or polypropylene) will have a rough or textured surface, which will enable a better “grip” by a cam cleat. A “monofilament” rope (as used in fishing lines, to make it harder for fish to see a line attached to a lure or bait) would not be used in this type of setting.
Because of the design and arrangement of cam cleat 40, as illustrated in FIG. 2, rope 49 can be pulled through cam cleat 40 in only one direction, shown by the block arrow, with little or no resistance. However, if the rope tries to travel in the opposite direction, through the cam cleat, the teeth 42b and 44b on the non-circular cammed surfaces of the two gears 42 and 44 will “bite into” the rope, in a manner which prevents travel of the rope in the “blocked” or prohibited direction. As the teeth on the two gears 42 and 44 rotate slightly in the “not allowed” direction, due to a pulling action exerted by the surface of the rope, the ridges of those surfaces will be pulled closer together, because of the non-circular cammed shape of gears 42 and 44. This will cause the gear teeth to “bite” even harder into the rope. This generates a powerful squeezing and gripping force, and if the rope is pulled even harder, the gears of the cam cleat will be pulled even closer together, causing the cleat to grip the rope even more tightly than before.
In a typical cam cleat on a sailboat, the cam cleat will have either: (1) an open top surface, to allow someone to quickly release the rope from the cleat, by jerking the rope in an upward direction, at a location near the cleat; or, (2) a specialized constraining bracket, which will require the rope to be pulled upward in a specific manner, before the rope will be released by the two cam gears. That type of constraining bracket can reduce the risk of accidental release of a rope at an unwanted and possibly dangerous time.
The risk of accidental release of a rope, by a cam cleat, merits attention. In general, on sailboats, cam cleats without adjacent fixed cleats are used only for temporarily securing ropes that are called “sheets”. This set of ropes is used to trim the sails (i.e. they are used to pull sails and booms in horizontal directions). By contrast, any ropes that are used to raise or lower sails or booms (or other devices), in a vertical direction, are referred to as “halyards”. The distinction between “sheets” and “halyards” is crucially important, and it is taught in any beginning class on sailing.
Halyards are not used nearly as frequently as sheets, and a sudden failure of a halyard would be more likely to cause a serious and perhaps catastrophic problem or failure, up to and including sinking of a boat, and loss of life. Therefore, if a cam cleat is included in the mechanism that is used to raise a halyard on a small sailboat, a fixed cleat can be positioned next to the cam cleat. This arrangement will allow a sailor to get a secure grip on a halyard, pull hard on it to raise a sail a limited distance, and then let go of the halyard for a moment, in order to grab the halyard at a spot closer to the mast, to provide a better grip and better leverage for the next tug on the rope. Accordingly, the type of ratcheting control that is provided by a cam cleat allows someone to raise a sail all the way up a mast, by means of a series of short pulls on a halyard rope. Once the sail has been raised, the halyard is secured to a fixed cleat mounted next to the cam cleat, to ensure that the rope cannot be released accidentally.
Alternately, a sailor on a small sailboat can simply wrap the free end of a halyard rope around the mast, and lightly tie the rope to the mast, using a simple knot. The act of securing the rope close to the mast will effectively cause the rope to remain near the bottom of the cam cleat gears, and will help ensure that the rope will not be lifted and raised, somehow, out of the grip of the gears in the cam cleat.
In contrast to halyards, which raise and lower things vertically on a boat, cam cleats are frequently used to pull and secure “sheet” ropes on a sailboat, despite the well-known and well-recognized risks that cam cleats (especially “open top” cam cleats) sometimes fail. Skilled sailors must learn to accept and respect those risks; for example, if they hear a suspicious sound which indicates that something might be going wrong, they are taught to duck, immediately, rather than stand up and look around, in case a cam-cleat has failed and has allowed a fast-moving boom to swing around unexpectedly. There are plenty of references to sailors “taking swimming lessons” if they fail to recognize and respect the risk that a cam cleat might fail and release a rope it was holding.
Other types of mechanical ratcheting systems are also known. For example, some types of cam cleats have a single non-circular gear which can rotate; when the rope attempts to pull that gear in the non-allowed direction, the teeth on the non-circular gear will press the rope harder and harder into a constrained channel which has non-moving but ridged gripping surfaces. These types of single-gear cam cleats can be found on adjustable bungee cords and various other devices.
Advantages of Racheting Anchors for Securing Cartilage Implants; Start-Snug-Tighten Procedures
When used to help anchor and reinforce surgical implants that are designed to replace damaged cartilage, one of the advantages that could be provided by ratcheting suture anchors—if such devices are developed and manufactured with sufficiently high levels of reliability, and sufficiently low risks and rates of failure—is that they would enable a surgeon to perform a type of installation procedure that would be very useful.
Those three steps can be summarized in the phrase, “start them all, then snug them all, then tighten them all”.
If desired, that phrase can be shortened to “start, snug, tighten”, so long as the reader understands that the entire “start” procedure must be finished for all of the sutures, before the second procedure should be started for any of the sutures. If each anchoring suture strand in a multi-strand system can progress through all three of the “start, snug, tighten” steps in a coordinated manner, then a single surgeon can perform an anchoring procedure that otherwise might require two or more people to achieve.
An example of how this type of approach can work, in a completely different field, involves replacing a flat tire, on a typical passenger automobile. After the car has been jacked up to remove the weight from the flat tire, the wheel (i.e., the steel or alloy “hub” component), with the tire that has gone flat still affixed to the wheel, is pulled off of an assembly (usually called the “wheel mount”) which remains affixed to the car. A replacement wheel which carries a properly inflated tire must then be mounted, on the wheel mount.
In nearly all modern passenger cars, the wheel mount will have either four or five “studs” (i.e., threaded bolts) which protrude out from the wheel mount. Those studs will fit into accommodating holes on a wheel which is carried in the car, as a spare. The use of protruding studs on a wheel mount (rather than threaded holes, recessed into the wheel mount) allows any person who is replacing the wheel to lift the new wheel and tire slightly and place them onto the wheel mount, in a first step that does not involve any lug nuts. This makes it much easier to position a spare tire on a wheel mount, than would be required if a person had to hold a wheel and tire at an exact stationary height, while also struggling to get the end of a bolt inserted and then properly seated and started, in a recessed threaded hole.
Once the new wheel with the spare tire is in place, with all four or five studs passing through accommodating holes in the wheel, it is not good practice to screw on and then fully tighten a first lug nut, and then screw on and fully tighten a second lug nut, and then a third, and fourth, etc. Instead, each and every one of the lug nuts should progress through a “start them all, then snug them all, then tighten them all” routine, by the person replacing the flat tire.
In this context, “start” refers to getting each threaded lug nuts properly started on a threaded stud, with the threads of the nut and the stud properly engaged with each other, so that it will not damage either the nut or the stud, when the nut is forcibly screwed onto the stud.
After all four (or five) of the lug nuts have been fully and properly “started” on the studs, the next step is to get all four (or five) lug nuts properly “snugged”. This term refers to a process in which the fingers (and possibly a wrench, using low force) are used to screw the nuts farther onto the studs, until a beveled or rounded surface on the inner side of each lug nut has become properly “seated” against the corresponding beveled or rounded surface of a hole in the wheel. That “snugging” step cannot and will not be accomplished in a secure and reliable manner, if the operator: (i) fully tightens a first lug nut, while all of the other lug nuts remain loose; and then, (ii) fully tightens a second lug nut, while the remaining lug nuts remain loose; and then, (iii) fully tightens a third lug nut, etc.
Instead, the process of properly “seating” and securing the entire wheel-and-tire assembly, to the wheel mount, is crucially important. That process can be accomplished, with much higher levels of safety and security, by “snugging” all of the nuts against the wheel holes, before any of the nuts are fully tightened.
Finally, after all lug nuts have been fully “snugged”, with a modest but substantial level of tightness to ensure that the entire wheel has been properly “seated” on the wheel mount, the best way to fully tighten the lug nuts is by using a “bracketing” or “opposites” sequence. As soon as a first lug nut has been fully tightened, the next lug nut which should be tightened should be on the opposite side of the wheel (or as close to opposite as possible, if the wheel has five holes). By doing the first two tightening operations on two lug nuts which are as far apart from each other as possible, a person replacing a flat tire can make sure there is no “last second settling” or other shifting, pulling, or other motion which might raise questions about whether the new wheel is fully and properly seated on the wheel mount.
Accordingly, the entire process can be summarized as “start them all, then snug them all, then tighten them all”; or, in even shorter form, that entire sequence can be referred to as, “start, snug, tighten”, so long as a listener or reader understands the full sequence.
Returning to the subject of suture anchors used during surgery, if knotless suture anchors with ratcheting mechanisms can be developed and mass-manufactured with sufficiently high levels of reliability and safety (which will require very low or non-existent failure rates), then those types of ratcheting anchors can enable a directly comparable “start, then snug, then tighten” installation procedure, for use with relatively large cartilage-replacing implants. Each and all of the multiple suture strands which will be used, to help securely anchor a cartilage-replacing implant to a bone, can and should go through a “start, then snug, then tighten” cycle of steps.
In this type of procedure, each and all of the suture anchors that will be used to help anchor an implant to a bone, in a load-bearing joint such as a knee, should be properly “started” (i.e., emplaced into the supporting bone) before any of the suture strands are pulled “snug”, since any prematurely “snug” strand might distort or misalign a flexible implant, or otherwise render it more difficult for the surgeon to emplace all of the anchors in truly optimal positions.
After all of the anchors and strands have been “started”, they should all be “snugged”, in a manner which will provide gentle yet reliable assurance that the implant has become fully seated in its final desired position on the bone, with no unwanted distortions caused by any particular anchoring strand.
After all of the anchoring strands have been properly tensioned to a balanced and symmetric level of “snugness” around the full periphery of the implant, the final tightening steps should be carried out, preferably in a sequence that preserves a properly balanced load distribution, by initial selection and tightening of suture strands that are positioned on opposing or “bracketing” sides or ends of the implant.
Once that type of installing, anchoring, and reinforcing procedure is understood, and after certain types of candidate ratchet mechanisms have been explained and illustrated, then certain advantages, benefits, and improvements that can be provided the ratcheting system disclosed herein, compared to the prior ratcheting system disclosed in the two Van der Burg applications, will begin to become clear. Those advantages will be discussed below, after the mechanisms themselves have been explained and illustrated.
Accordingly, one object of this invention is to disclose one or more ratcheting mechanisms, for incorporation into knotless suture anchors, which will provide sufficiently high levels of security, stability, and reliability to justify and enable their use in surgical implantation of surgical implants that contain specialized surfaces which promote tissue ingrowth, for stronger and more stable anchoring purposes, over a span of weeks or months.
Another object of this invention is to disclose and provide methods for improved anchoring of surgical implants that contain tissue-ingrowth surfaces, using a combination of: (i) suture segments which emerge from such implants, and (ii) knotless ratcheting-type suture anchors as described herein, which are designed to allow surgeons to tension and tighten, in a staged, sequential, and controlled manner, each of the suture segments that emerge from various locations around the periphery of an implant.
Another object of this invention is to disclose designs which are believed to be novel, for knotless suture anchors that have ratcheting mechanisms which will allow surgeons to tension and tighten, in a staged, sequential, and controlled manner, each of a number of suture segments that will be used to anchor and reinforce a surgical implant device, especially among implant devices that contain surfaces which promote tissue ingrowth.
These and other objects of the invention will become more apparent through the following summary, drawings, and detailed description.